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Xsession(5)                   File Formats Manual                  Xsession(5)

       Xsession - initialize X session

       Xsession [ session-type ]

       /etc/X11/Xsession is a Bourne shell (sh(1)) script which is run when an
       X Window System session is begun by startx(1x)  or  a  display  manager
       such  as  xdm(1x).   (Some  display  managers only invoke Xsession when
       specifically directed to so by the user; see the documentation for your
       display  manager to find out more.)  Administrators unfamiliar with the
       Bourne shell will likely  find  the  Xsession.options(5)  configuration
       file easier to deal with than Xsession itself.

       Xsession  is  not  intended  to  be invoked directly by the user; to be
       effective it needs to run in a special environment  associated  with  X
       server  initialization.  startx, xdm, xinit(1x), and other similar pro-
       grams handle this.

       By default on a Debian system, Xsession is used by both common  methods
       of starting the X Window System, xdm (or another X display manager) and
       startx.  To change this  for  xdm,  edit  the  'DisplayManager*session'
       resource  in the /etc/X11/xdm/xdm-config file -- for other display man-
       agers, consult their documentation.  To stop startx from using Xsession
       by default, replace the contents of the /etc/X11/xinit/xinitrc file.

       The  Xsession  script is quite flexible, and extensive customization of
       the X startup  procedure  is  possible  without  modifying  the  script
       itself.  See "CUSTOMIZING THE STARTUP PROCEDURE" below.

       Xsession may optionally be passed a single argument indicating the type
       of X session to be started.  It is up to the display manager to set the
       argument.   To   pass  Xsession  an  argument  from  startx  or  xinit,
       /etc/X11/Xsession (or /etc/X11/xinit/xinitrc) must be called explicitly
       with  a  path,  as  in  startx /etc/X11/Xsession failsafe.  By default,
       three different arguments are supported:

              invokes a session consisting solely of an x-terminal-emulator(1)
              (no  window  manager  is  launched).  If the x-terminal-emulator
              program cannot be found,  the  session  exits.   The  'failsafe'
              argument  is  ignored  if  there  is no 'allow-failsafe' line in

              produces the same behavior as if no session  type  argument  had
              been given at all.

              starts program if it can be found in the $PATH.  This is usually
              a session manager or a very featureful window manager.  If  pro-
              gram is not found, the Xsession script proceeds with its default
              behavior.   This  argument   is   ignored   if   there   is   no
              'allow-user-xsession'  line in Xsession.options.  (If the admin-
              istrator does not want users writing their own .xsession  files,
              it  makes  little  sense  to permit them to specify the names of
              arbitrary programs to run.)  Note that the  restriction  may  be
              easy to bypass, e.g. by using a .gnomerc file instead.

       Initially,  Xsession  performs some housekeeping.  It declares a set of
       built-in functions (see "BUILT-IN SHELL  FUNCTIONS"  below)  and  vari-
       ables,  then attempts to create a log file for the X session, or append
       to an existing one.  Historically this is called an 'error'  file,  but
       it catches all sorts of diagnostic output from various X clients run in
       the user's session, not just error messages.  If it  is  impossible  to
       write  to  an  error  file, the script (and thus the X session) aborts.
       For convenience, once the error file is successfully  opened,  Xsession
       reports  the  fact that the session has started, the invoking username,
       and the date to the error file.  This makes it easier to discern  which
       X session produced a particular line of output in the file.

       Xsession  next  confirms that its script directory, Xsession.d, exists.
       If it does not, the script aborts.  After the script directory is  con-
       firmed  to  be present, Xsession uses run-parts(1) to identify files in
       that directory that should be sourced (executed) in the  shell's  envi-
       ronment.   Only  files  named  in  a  certain  way are sourced; see the
       run-parts manual page for a description  of  valid  characters  in  the
       filename.   (This restriction enables the administrator to move experi-
       mental or problematic files out of the way of the script but keep  them
       in  an  obvious  place,  for  instance  by renaming them with '.old' or
       '.broken' appended to the filename.)

       Five shell script portions  are  supplied  by  default  to  handle  the
       details of the session startup procedure.

              Arguments  are  processed as described in "SESSION TYPES" above.
              The startup program, if one is  identified  at  this  point,  is
              merely stored for later reference, and not immediately executed.

              X  resources  are merged.  run-parts is again used, this time to
              identify files in the /etc/X11/Xresources directory that  should
              be   processed   with   'xrdb   -merge'.    Next,  if  the  line
              'allow-user-resources'  is  present  in  Xsession.options,   the
              user's $HOME/.Xresources file is merged in the same way.

              Source  global  environment  variables.  This script will source
              anything in $HOME/.xsessionrc  if  the  file  is  present.  This
              allows  the user to set global environment variables for their X
              session, such as locale information.

              Determine startup program.  The X client to launch as  the  con-
              trolling  process  (the  one  that,  upon  exiting, causes the X
              server to exit as well) is determined next.   If  a  program  or
              failsafe  argument  was  given and is allowed (see above), it is
              used  as  the  controlling  process.   Otherwise,  if  the  line
              'allow-user-xsession'   is   present   in   Xsession.options,  a
              user-specified session program or script is used.  In the latter
              case,  two historically popular names for user X session scripts
              are searched for: $HOME/.xsession and $HOME/.Xsession (note  the
              difference  in  case).   The  first  one  found is used.  If the
              script is not executable, it is marked to be executed  with  the
              Bourne  shell  interpreter,  sh.   Finally, if none of the above
              succeeds,   the   following   programs   are    searched    for:
              /usr/bin/x-session-manager,    /usr/bin/x-window-manager,    and
              /usr/bin/x-terminal-emulator.  The first one found is used.   If
              none are found, Xsession aborts with an error.

              Start  ssh-agent(1),  if needed.  If the line 'use-ssh-agent' is
              present in Xsession.options, and no SSH agent process appears to
              be  running  already,  ssh-agent is marked to be used to execute
              the startup program determined previously.  Note: this function-
              ality may move to the ssh package in the future.

              Start  the X session.  The startup program is executed, inside a
              Bourne shell if it is not executable, and inside an ssh-agent if
              necessary.   The shell's exec command is used to spare a slot in
              the process table.

       Of course, any of the existing files can be edited in place.

       Because the order in which the various scripts  in  /etc/X11/Xsession.d
       are  executed  is important, files to be added to this directory should
       have a well-formed name.  The following format is recommended:

       * a two-digit number denoting sequence;

       * the name of  the  package  providing  the  script  (or  'custom'  for
       locally-created scripts);

       * an underscore;

       *  a  description of the script's basic function, using only characters
       allowed by run-parts.

       Here is an example of how  one  might  write  a  script,  named  40cus-
       tom_load-xmodmap, to invoke xmodmap(1x):


       if [ -x /usr/bin/X11/xmodmap ]; then
           if [ -f "$SYSMODMAP" ]; then
               xmodmap "$SYSMODMAP"

       if [ -x /usr/bin/X11/xmodmap ]; then
           if [ -f "$USRMODMAP" ]; then
               xmodmap "$USRMODMAP"

       Those  writing  scripts for Xsession to execute should avail themselves
       of its built-in shell functions, described below.

       message is used for communicating with the user.  It is a  wrapper  for
       the  echo(1)  command and relies upon echo for its argument processing.
       This function may be given an arbitrarily long message string, which is
       formatted  to  the user's terminal width (breaking lines at whitespace)
       and sent to standard error.  If the DISPLAY environment variable is set
       and  the  xmessage(1x)  program  is available, xmessage is also used to
       display the message.

       message_nonl is used for communicating with the user  when  a  trailing
       newline  is  undesirable;  it omits a trailing newline from the message
       text.  It otherwise works as message.

       errormsg is used for indicating an error  condition  and  aborting  the
       script.   It  works as message, above, except that after displaying the
       message, it will exit Xsession with status 1.

       The following environment variables affect the execution of Xsession:

       HOME   specifies the user's home directory; various files are  searched
              for here.

       TMPDIR names a default directory for temporary files; if the standard X
              session error file cannot be opened, this variable  is  used  to
              locate a place for one.

              indicates the width of terminal device in character cells.  This
              value is used for formatting diagnostic messages.

              is a directory containing Bourne shell scripts to be executed by
              Xsession.   Files  in this directory are matched using run-parts
              and are sourced, not executed in a subshell.

              is a directory containing files corresponding to Debian  package
              names,  each  of  which contains system-wide X resource settings
              for X clients from the corresponding package.  The settings  are
              loaded  with  xrdb  -merge.  Files in this directory are matched
              using run-parts.

              contains configuration options for the /etc/X11/Xsession script.
              See Xsession.options(5) for more information.

              contains  X  resources  specific to the invoking user's environ-
              ment.  The settings are loaded  with  xrdb  -merge.   Note  that
              $HOME/.Xdefaults  is a relic from X Version 10 (and X11R1) days,
              before app-defaults files were implemented.  It has been  depre-
              cated  for  over  ten  years at the time of this writing.  .Xre-
              sources should be used instead.

              is a sequence of commands invoking X clients (or a session  man-
              ager  such  as xsm(1x)).  See the manual page for xinit for tips
              on writing an .xsession file.

              is where standard output and standard error for Xsession  script
              and all X client processes are directed by default.

              is  where  the  X  session  error file is placed if $HOME/.xses-
              sion-errors cannot be opened.  For security reasons,  the  exact
              filename is randomly generated by tempfile(1).

       Stephen  Early,  Mark Eichin, and Branden Robinson developed Debian's X
       session handling scripts.  Branden Robinson wrote this manual page.

       Xsession.options(5),  X(7x),  run-parts(1),  ssh-agent(1),  startx(1x),
       tempfile(1), xdm(1x), xmessage(1x), xmodmap(1x), xrdb(1x), sh(1)

Debian Project                    2004-11-04                       Xsession(5)